A storage device is managed by a RAID (Redundant Array of Inexpensive Disks) method, and includes a plurality of disk devices arranged in an array and a control unit that controls the plurality of disk devices. A storage device is connected to a host computer such as a server (hereinafter also referred to as a host server), and provides a logical storage area (hereinafter also referred to as a logical volume) arranged so as to be redundant based on a RAID structure.
In recent years, the amount of data to be managed by corporations and the like is increasing on a daily basis. Accordingly, storage devices have become increasingly larger in scale, resulting in an increase in power consumption. In addition, there is an upward trend in the number of electronic devices including storage devices to be installed at a data center or the like, and the power consumption by an entire data center is also on the rise. In the present description, an electronic device refers to a device that becomes operational through energization.
Meanwhile, as the power consumption of electronic devices increases, the amount of released heat also increases, which in turn causes an increase in the power consumption of cooling facilities at the data centers.
When charging a user for electricity used by an electronic device installed by the user at a data center, a data center provider may prescribe, in advance, an upper limit on the electric energy to be supplied to one or more electronic devices used by the user within a specific period (usually the contract period). When the electric energy consumed by the user during the aforementioned period exceeds the electric energy upper limit prescribed in advance, the data center provider may additionally bill an extra charge for the exceeded electric energy. Electric energy refers to a value calculated as a summation of the accumulated products of power and time.
Various electronic devices to be installed at a data center or the like include electronic devices capable of shifting from a normal operational state to a power-saving state, as well as electronic devices equipped with an energized part capable of reducing power consumption compared to a normal operational state during suspension of energization or the like and which have a power-saving function realized by performing operational control of the energized part.
For example, a technique for limiting power consumption by a storage device included in an electronic device is disclosed in Patent Citation 1. Patent Citation 1 discloses a technique which predicts, upon activation of a disk device, the power consumption after activation, determines whether or not the predicted power consumption exceeds a preset threshold, and controls activation and suspension of the disk device according to the determination. According to Patent Citation 1, by controlling activation and suspension of the disk device, the power consumption of the storage device can be limited to or below a preset threshold and, consequently, the power consumption by the storage device can be reduced.